JP5927057B2 - Liquid crystal display - Google Patents

Description

  The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device using polymer dispersed liquid crystal (PDLC).

  The PDLC is a light scattering type liquid crystal display device that scatters incident light using a difference in refractive index between a polymer network and a liquid crystal. Therefore, a polarizing plate used in an LCD (Liquid Crystal Display) is unnecessary, and it is not necessary to form an alignment film for aligning liquid crystal molecules. Therefore, light loss is extremely small and bright display is possible.

  PDLC has a structure in which liquid crystals are phase-separated in a polymer (polymer network) formed in a three-dimensional network, and a state in which liquid crystal molecules are randomly arranged along the side wall of the polymer network and an electric field. When applied, the liquid crystal molecules are arranged in the electric field direction to create a light scattering state and a light transmission state, respectively. The degree of scattering is determined by the voltage applied to the liquid crystal, and the voltage applied to the liquid crystal is determined by the partial pressure between the polymer material and the liquid crystal.

  FIG. 17 is a graph showing the relationship between voltage and transmittance at a plurality of types of temperatures (as an example, −10 ° C., 25 ° C., and 50 ° C.) by replacing the degree of scattering with transmittance. As can be understood from FIG. 17, the transmittance at the same voltage varies greatly with temperature. The cause of this is that the dielectric constant of the liquid crystal is small when the temperature is high, and conversely, the dielectric constant is large when the temperature is low. For this reason, since the effective voltage applied to the liquid crystal is divided by the polymer material, the effective voltage is high when the temperature is high, and the effective voltage is low when the temperature is low. Therefore, the PDLC characteristics vary greatly with temperature as shown in FIG.

  When the binary display of scattering and transmission is performed, the display is not affected even if the temperature changes. However, when the halftone is displayed by the voltage, the transmittance greatly changes depending on the temperature. For example, when the voltage is 2.2 V, the transmittance is 50% at 25 ° C., but the transmittance is 86% at 50 ° C., the transmittance is 5% at −10 ° C., and the halftone is 50 ° C. and −10 ° C. There is a problem that it cannot be expressed and is in the same level as a binary display.

  Patent Document 1 discloses a technique for displaying halftones by dithering.

Japanese translation of PCT publication No. 2003-533751

  The present invention provides a liquid crystal display device capable of halftone display in a wide temperature range.

A liquid crystal display device according to an aspect of the present invention is a liquid crystal display device capable of displaying first and second characters, and includes first and second substrates and a first substrate provided on the first substrate. 1 lower display electrode, a first insulating layer provided on the first lower display electrode, and a first pattern comprising a mesh pattern provided on the first insulating layer and having a plurality of openings. An upper display electrode, a first counter electrode provided on the first insulating layer, a second lower display electrode provided on the second substrate, and the second lower display electrode A second insulating layer provided on the second insulating layer, a second upper display electrode provided on the second insulating layer and having a mesh pattern having a plurality of openings, and provided on the second insulating layer a second counter electrode is, said first upper display electrode and the second opposing electrode are opposed, and the ; And a second upper display electrode and the first of said opposed electrode is in a state of opposing first and polymer dispersed sandwiched second substrate liquid crystal layer, the first character, the second 1 lower display electrode, the first upper display electrode, and the second counter electrode. The second character is the second lower display electrode, the second upper display electrode, and the first It is characterized by being comprised from this counter electrode.

  According to the present invention, a liquid crystal display device capable of halftone display in a wide temperature range can be provided.

The top view and side view of the liquid crystal display device which concern on this embodiment. 1 is a cross-sectional view of a liquid crystal display device according to an embodiment. The top view explaining the pattern of an upper display electrode. Schematic explaining the orientation state of a polymer dispersion type liquid crystal layer at the time of voltage control. Voltage waveform in the transparent state. Voltage waveform in the scattering state. Voltage waveform in the first halftone. Voltage waveform in the second halftone. The graph which shows the relationship between the area ratio of the upper display electrode with respect to a lower display electrode, and the transmittance | permeability. 4 is a plan view of an upper display electrode of a character according to Configuration Example 1. FIG. FIG. 11 is a cross-sectional view of the liquid crystal display device along the line AA ′ shown in FIG. 10. The top view of the character which concerns on the example 2 of a structure. Sectional drawing of the liquid crystal display device along the AA 'line shown in FIG. The top view of the upper display electrode of the character which concerns on a comparative example. Sectional drawing of the liquid crystal display device which concerns on a comparative example. Schematic which shows the example of routing of the wiring provided in the board | substrate. The graph which shows the relationship between the voltage and the transmittance | permeability in a polymer dispersion type liquid crystal.

  Hereinafter, embodiments will be described with reference to the drawings. However, it should be noted that the drawings are schematic or conceptual, and the dimensions and ratios of the drawings are not necessarily the same as the actual ones. Further, even when the same portion is represented between the drawings, the dimensional relationship and ratio may be represented differently. In particular, the following embodiments exemplify an apparatus and a method for embodying the technical idea of the present invention, and the technical idea of the present invention depends on the shape, structure, arrangement, etc. of components. Is not specified. In the following description, elements having the same function and configuration are denoted by the same reference numerals, and redundant description will be given only when necessary.

[1] Configuration of Liquid Crystal Display Device A liquid crystal display device according to an embodiment of the present invention is a light scattering type liquid crystal display device that scatters incident light using a difference in refractive index between a polymer network and liquid crystal. . In addition, the liquid crystal display device according to the present embodiment is a pattern display type liquid crystal display device capable of displaying a plurality of characters including characters, figures, patterns, and the like. FIG. 1 is a plan view and a side view of a liquid crystal display device 1 according to the present embodiment.

  A polymer-dispersed liquid crystal layer is provided between the substrates 10 and 11. The polymer-dispersed liquid crystal layer is sandwiched between the substrates 10 and 11 and is sealed between the substrates 10 and 11 by a sealing material 12. A region surrounded by the sealing material 12 is a display region DA of the liquid crystal display device 1, and a polymer dispersed liquid crystal layer is provided in the display region DA. The substrate 10 is provided with a plurality of terminals 13 electrically connected to electrodes for displaying characters. The terminal 13 is connected to a drive circuit (not shown) for applying a voltage to an electrode for displaying a character.

  In the display area DA of FIG. 1, as an example of the character CR, a plurality of square patterns, and circle, triangle, and square patterns are shown. A square pattern represents a focus point to be displayed on a camera finder or the like. The pattern of the character CR can be arbitrarily designed. In addition, a crop frame CF is provided in the display area DA. The crop frame is used to change the size of the image, and the aspect ratio of the displayed image can be changed by masking a part of the display area with the crop frame. The shape and position of the crop frame can be arbitrarily designed.

  FIG. 2 is a cross-sectional view of the liquid crystal display device 1 according to the present embodiment. A lower display electrode 20 is provided on the upper surface (surface on the liquid crystal side) of the substrate 10. An insulating layer 21 is provided on the upper surface of the substrate 10 so as to cover the lower display electrode 20. An upper display electrode 22 and a counter electrode 23 are provided on the insulating layer 21.

  A lower display electrode 30 is provided on the upper surface (surface on the liquid crystal side) of the substrate 11. An insulating layer 31 is provided on the upper surface of the substrate 11 so as to cover the lower display electrode 30. An upper display electrode 32 and a counter electrode 33 are provided on the insulating layer 31. In addition, the upper part here means the direction which goes to a liquid crystal on the basis of a board | substrate. The bottom surface of the substrate 11 (the surface opposite to the surface on the liquid crystal side) is the image display surface of the liquid crystal display device 1.

  A unit composed of the lower display electrode 20, the upper display electrode 22, and the counter electrode 33 displays one character CR1 or a part of one character CR1. Further, the unit composed of the lower display electrode 30, the upper display electrode 32, and the counter electrode 23 displays one character CR2 or a part of one character CR2. That is, the lower display electrode and the upper display electrode for displaying one character are provided on the substrates 10 and 11, respectively. Each of the upper display electrodes 22 and 32 has a mesh pattern having a plurality of openings. On the other hand, the lower display electrodes 20 and 30 and the counter electrodes 23 and 33 do not have a mesh pattern. The lower display electrode 20 and the upper display electrode 22 have the same shape (outer shape).

  The liquid crystal display device 1 displays a halftone between the transparent state and the scattering state by dithering using the upper display electrode and the lower display electrode. As a method of displaying one character, there are (1) a method of processing the lower display electrode 20 and the upper display electrode 22 into a character pattern, and (2) a method of processing the counter electrode 33 into a character pattern. In the case of the method (1), the counter electrode 33 is processed so as to have a size equal to or larger than that of the upper display electrode 22. In the case of the method (2), the lower display electrode 20 and the upper display electrode 22 are processed to have the same size as or larger than the counter electrode 33. The same applies to the case where characters are displayed on the lower display electrode 30, the upper display electrode 32, and the counter electrode 23.

  A plurality of wirings 24 electrically connected to the lower display electrode 20, the upper display electrode 22, and the counter electrode 23 are provided on the upper surface (the liquid crystal side surface) of the substrate 10. Each of the upper display electrode 22 and the counter electrode 23 is electrically connected to a corresponding wiring 24 through a contact plug 25 provided in the insulating layer 21. Each of the plurality of wirings 24 is electrically connected to the drive circuit 41 via the terminal 13 shown in FIG.

  A plurality of wirings 34 electrically connected to the lower display electrode 30, the upper display electrode 32, and the counter electrode 33 are provided on the upper surface (surface on the liquid crystal side) of the substrate 11. Each of the upper display electrode 32 and the counter electrode 33 is electrically connected to a corresponding wiring 34 through a contact plug 35 provided in the insulating layer 31. Each of the plurality of wirings 34 is electrically connected to the drive circuit 41 via the terminal 13 shown in FIG.

  A polymer-dispersed liquid crystal layer 40 is provided between the substrates 10 and 11. Specifically, the polymer-dispersed liquid crystal layer 40 is sandwiched between the substrates 10 and 11 arranged so that the upper display electrode 22 and the counter electrode 33 face each other. The polymer dispersed liquid crystal layer 40 is sealed between the substrates 10 and 11 by the sealing material 12, and the sealing material 12 adheres the substrates 10 and 11. The thickness (gap) of the polymer dispersed liquid crystal layer 40 is, for example, about 7 μm.

  The polymer-dispersed liquid crystal layer 40 includes, for example, a mixed solution of nematic liquid crystal having a positive dielectric anisotropy and a polymer material that undergoes a polymerization reaction by light between substrates, and the polymer of the mixed solution is irradiated with light. It is formed by photopolymerizing the material to phase-separate the polymer and the liquid crystal. Thus, the polymer dispersed liquid crystal layer 40 has a structure in which liquid crystals are phase-separated in a polymer (polymer network) formed in a three-dimensional network.

  Each of the substrates 10 and 11 is a transparent substrate made of glass, quartz, plastic, or the like. Each of the lower display electrode, the upper display electrode, the counter electrode, the wiring, and the contact plug is formed of a transparent electrode, and for example, ITO (indium tin oxide) is used. The film thicknesses of the lower display electrode, the upper display electrode, and the counter electrode are each about 25 nm, for example. As the insulating layers 21 and 31, for example, silicon nitride is used. The film thicknesses of the insulating layers 21 and 31 are each about 500 nm, for example.

  FIG. 3 is a plan view for explaining a pattern of the upper display electrode 22. The configuration of the upper display electrode 32 is the same as that in FIG.

  The upper display electrode 22 has a mesh pattern having a plurality of openings 22A. The shape of the opening 22A may be a circle as shown in FIG. 3, an ellipse, a quadrangle, or another polygon. As described above, since the lower display electrode 20 and the upper display electrode 22 have the same outer shape, the lower display electrode 20 is always provided below the opening 22A. The diameter D of the opening 22A is, for example, about 50 μm, and the distance S between the openings is, for example, about 18 μm.

  In the present embodiment, halftones are displayed by dithering the lower display electrode 20 and the upper display electrode 22. Therefore, in order to make the halftone display uniform, it is desirable that the openings 22A formed in the upper display electrode 22 are uniformly arranged. In the present embodiment, the opening 22A formed in the upper display electrode 22 has a staggered arrangement. A staggered arrangement is a plurality of openings arranged in the next row at a position half the distance between two adjacent openings or the distance between the centers of two adjacent openings (referred to as pitch). This is a pattern in which the openings are arranged. When a staggered arrangement is used as the pattern of the opening 22A formed in the upper display electrode 22, it is possible to prevent display unevenness from occurring in a halftone due to dithering.

[2] Operation of Liquid Crystal Display Device 1 Next, the operation of the liquid crystal display device 1 will be described. The image display operation of the liquid crystal display device 1 is controlled by the drive circuit 41.

  The drive circuit 41 is electrically connected to the lower display electrode 20, the upper display electrode 22 and the counter electrode 33, applies a binary voltage between the lower display electrode 20 and the counter electrode 33, and also displays the upper display electrode. A binary voltage is applied between 22 and the counter electrode 33. As a result, the lower display electrode 20 and the upper display electrode 22 can be independently voltage controlled. Similarly, the drive circuit 41 is electrically connected to the lower display electrode 30, the upper display electrode 32, and the counter electrode 23, applies a binary voltage between the lower display electrode 30 and the counter electrode 23, and A binary voltage is applied between the upper display electrode 32 and the counter electrode 23. As a result, the lower display electrode 30 and the upper display electrode 32 can be independently voltage controlled. In the following example, the display operation related to the unit composed of the lower display electrode 20, the upper display electrode 22 and the counter electrode 33 will be described. It is the same.

  FIG. 4 is a schematic diagram for explaining the alignment state of the polymer dispersed liquid crystal layer 40 during voltage control. 4A is a diagram for explaining the scattering state of the polymer dispersed liquid crystal layer 40, and FIG. 4B is a diagram for explaining the transmissive state of the polymer dispersed liquid crystal layer 40. As shown in FIG. In FIG. 4, a part of the polymer dispersed liquid crystal layer 40 sandwiched between the upper display electrode 22 and the counter electrode 33 is extracted and shown.

  When no voltage is applied to the polymer-dispersed liquid crystal layer 40 (the voltage is set to 0 V), no electric field is applied to the liquid crystal molecules, and the liquid crystal molecules are randomly arranged. Therefore, when white light is incident on the polymer-dispersed liquid crystal layer 40, the incident light is scattered and observed as a cloudy state from the outside. On the other hand, when a high voltage (for example, 5 V) is applied to the polymer dispersed liquid crystal layer 40, the liquid crystal molecules are aligned in the electric field direction. Therefore, when white light is incident on the polymer-dispersed liquid crystal layer 40, the incident light is transmitted and observed as a transparent state from the outside.

  In the present embodiment, since the lower display electrode 20 exists below the opening 22A of the upper display electrode 22, the polymer dispersed liquid crystal layer in the first region in which the upper display electrode 22 and the counter electrode 33 face each other directly It is possible to independently control the transmission state with the polymer dispersed liquid crystal layer in the second region in which the lower display electrode 20 and the counter electrode 33 face each other directly. Therefore, when displaying one character, dithering between the first area and the second area enables four types of display: transparent, two types of halftones (weak scattering 1 and 2), and scattering. .

  FIG. 5 is a voltage waveform in the transparent state. In the transparent state, the drive circuit 41 applies 5 V between the upper display electrode 22 and the counter electrode 33, and similarly applies 5 V between the lower display electrode 20 and the counter electrode 33. Thereby, since 5V is applied to the whole character, the whole character can be made into a transparent state. In addition, since the liquid crystal deteriorates when the DC voltage is continuously applied to the liquid crystal, the inversion drive that inverts the polarity of the voltage every certain time is applied. The period for performing the inversion driving can be designed as appropriate depending on the material of the liquid crystal, and is, for example, “1/30” seconds in this embodiment.

  FIG. 6 is a voltage waveform in the scattering state. In the scattering state, the drive circuit 41 makes 0 V between the upper display electrode 22 and the counter electrode 33, that is, sets the upper display electrode 22 and the counter electrode 33 to the same potential, and similarly, 0 V between the lower display electrode 20 and the counter electrode 33, That is, the upper display electrode 22 and the counter electrode 33 are set to the same potential. Thereby, since the electric field is not applied to the whole character, the whole character can be made into a scattering state.

  FIG. 7 is a voltage waveform in the first halftone (weak scattering state 1). In the weak scattering state 1, the drive circuit 41 applies 5 V between the upper display electrode 22 and the counter electrode 33, while setting 0 V between the lower display electrode 20 and the counter electrode 33. As a result, 5 V is applied to the first region of the character pattern in which the upper display electrode 22 and the counter electrode 33 face each other directly, and the electric field is applied to the second region in which the lower display electrode 20 and the counter electrode 33 face each other directly. Is not applied, the first region can be in a transparent state and the second region can be in a scattering state. Therefore, the first halftone by dithering can be displayed by the voltage control of FIG.

  FIG. 8 is a voltage waveform in the second halftone (weak scattering state 2). In the weak scattering state 2, the drive circuit 41 applies 0 V between the upper display electrode 22 and the counter electrode 33, while applying 5 V between the lower display electrode 20 and the counter electrode 33. As a result, no electric field is applied to the first region of the character pattern in which the upper display electrode 22 and the counter electrode 33 face each other, and the second region in which the lower display electrode 20 and the counter electrode 33 face each other directly. Since 5 V is applied, the first region can be in a scattering state and the second region can be in a transparent state. Therefore, the second halftone different from the first halftone can be displayed by the voltage control of FIG.

  In the present embodiment, the halftone transmittance is obtained by changing the size of the opening formed in the upper display electrode 22 or the distance between the openings, that is, the outer shapes of the lower display electrode 20 and the upper display electrode 22 are the same. In some cases, it can be controlled by changing the area ratio of the upper display electrode 22 to the lower display electrode 20. The area of the upper display electrode 22 here is a value obtained by subtracting the area of the opening from the area of the outer shape of the upper display electrode 22.

  FIG. 9 is a graph showing the relationship between the area ratio of the upper display electrode 22 to the lower display electrode 20 and the transmittance. FIG. 9 shows four waveforms of scattering, weak scattering 1, weak scattering 2, and transparency. The vertical axis in FIG. 9 represents transmittance (%), and the horizontal axis represents the area ratio of the upper display electrode 22 to the lower display electrode 20.

  As can be understood from FIG. 9, in the scattering state and the transparent state, a substantially constant transmittance can be maintained even if the area ratio changes. On the other hand, by changing the area ratio, it is possible to arbitrarily control the transmittance of halftone (weak scattering state 1 and weak scattering state 2). As described above, by appropriately setting the area ratio of the upper display electrode 22 to the lower display electrode 20 and performing the voltage control of FIGS. 5 to 8, it is possible to display the character in four different gradations.

  The condition of the opening 22A of the upper display electrode 22 is that when the diameter of the opening 22A is as small as 25 μm or less, the light is split by light diffraction and a rainbow can be seen, so the diameter of the opening 22A is 25 μm or more. It is desirable that In addition, when the diameter of the opening 22A is as large as 100 μm or more, the character display does not look uniform, and display irregularities such as, for example, dots appear. Therefore, the diameter of the opening 22A is preferably 100 μm or less. Furthermore, in order to further improve the uniformity of character display, the diameter of the opening 22A is desirably 50 μm or less.

[3] Character configuration example 1
Next, a specific configuration example of the character will be described.
FIG. 10 is a plan view of the upper display electrode of the character CR according to Configuration Example 1. FIG. FIG. 11 is a cross-sectional view of the liquid crystal display device 1 along the line AA ′ shown in FIG. The character CR shown in FIG. 10 is the square pattern shown in FIG. FIG. 10 and FIG. 11 are examples in which the character CR is configured by the upper display electrode 22 on the substrate 10 side, for example.

  The character CR having a square shape is represented by a lower display electrode 20 and an upper display electrode 22-1 having the same outer shape as the character CR. The line width of the letter B is, for example, 120 μm. The upper display electrode 22-1 has a mesh pattern having an opening 22A having a diameter of 50 μm, for example.

  In the region inside the character CR, an upper display electrode 22-2 having no opening is provided. An upper display electrode 22-3 having no opening is provided in a region outside the character CR. The upper display electrode 22-1 and the upper display electrode 22-2 are electrically separated by a gap GP, and the upper display electrode 22-1 and the upper display electrode 22-3 are electrically separated by a gap GP. Yes. The upper display electrodes 22-2 and 22-3 are electrically connected by a jumper JP and controlled by the same voltage. The counter electrode 33 is provided in a region facing the upper display electrodes 22-1 to 22-3.

  The character CR is displayed in four gradations of transparency, first halftone, second halftone, and scattering. Since the upper display electrodes 22-2 and 22-3 do not have openings, the inner and outer regions of the character CR are displayed with only two gradations of transparency and scattering.

  Since the line width of the character CR is as thin as about 120 μm, the opening of the upper display electrode 22-1 may be cut off halfway along the pattern edge of the character CR. Since the upper display electrode 22-1 does not exist in the area where the opening is cut, the alignment of the polymer dispersed liquid crystal layer 40 cannot be controlled by the upper display electrode 22-1 and the display of the pattern edge is easily blurred. In order to suppress the display blur of the pattern edge, it is desirable to trim the upper display electrode 22-1 along the pattern edge of the character CR. That is, the edge portion EG of the upper display electrode 22-1 is always provided at the pattern edge of the character CR. Thereby, since the orientation control of the polymer dispersed liquid crystal layer 40 can be performed at the pattern edge, display blur of the pattern edge can be suppressed.

[4] Character configuration example 2
Next, a specific configuration example of another character will be described.
FIG. 12 is a plan view of the character CR according to Configuration Example 2. FIG. 13 is a cross-sectional view of the liquid crystal display device 1 along the line AA ′ shown in FIG. The character CR shown in FIG. 12 is a round character CR arranged in the crop frame CF shown in FIG. 12 and 13 are examples in which the character CR is configured by the upper display electrode 32 on the substrate 11 side, for example.

  The lower display electrode 30 and the upper display electrode 32 have the same outer shape as the crop frame CF. The upper display electrode 32 has a mesh pattern. The lower display electrode 30 is electrically connected to the drive circuit 41 via the wiring 34, and the upper display electrode 32 is electrically connected to the drive circuit 41 via the contact plug 35 and the wiring 34. The counter electrode 23-1 has the same outer shape as the circular character CR. The counter electrode 23-2 has the same outer shape as the crop frame CF. The counter electrode 23-1 and the counter electrode 23-2 are electrically separated with a predetermined gap. Each of the counter electrodes 23-1 and 23-2 is electrically connected to the drive circuit 41 through the contact plug 25 and the wiring 24.

  The character CR displays four gradations of transparency, first halftone, second halftone, and scattering by controlling the voltages of the lower display electrode 30, the upper display electrode 32, and the counter electrode 23-1. Can do. Similarly, the crop frame CF controls the voltages of the lower display electrode 30, the upper display electrode 32, and the counter electrode 23-2 so that four gradations of transparent, first halftone, second halftone, and scattering are obtained. Can be displayed. (1) Only the crop frame CF is displayed by setting the character CR to the same gradation as the crop frame CF. (2) The character CR is displayed in the crop frame CF at a different gradation from the crop frame CF. (3) The crop frame CF is erased (transparent) and only the character CR is displayed, and (4) the crop frame CF and the character CR are erased.

  In the present embodiment, the gap between the character CR and the crop frame CF corresponds to a space between wirings. For example, assuming that the limit value (minimum processing dimension) of the wiring processing dimension caused by the manufacturing apparatus is a wiring width of 3 μm and a space of 3 μm, the gap between the character CR and the crop frame CF is the counter electrodes 23-1 and 23-. Corresponding to the space between the two, this gap is 3 μm. Thereby, even when the crop frame CF and the character CR are displayed in the same halftone, it is possible to prevent the boundary between the crop frame CF and the character CR from being visually recognized.

  FIG. 14 is a plan view of the upper display electrodes of the characters CR1 and CR2 according to the comparative example. FIG. 15 is a cross-sectional view of a liquid crystal display device according to a comparative example. In the comparative example, the adjacent characters CR1 and CR2 are formed using the lower display electrode 20 and the upper display electrode 22 formed on one substrate 10 side.

  The lower display electrode 20-1 and the upper display electrode 22-1 constituting the character CR1 have the same outer shape, and the upper display electrode 22-1 has a mesh pattern. Similarly, the lower display electrode 20-2 and the upper display electrode 22-2 constituting the character CR2 have the same outer shape, and the upper display electrode 22-2 has a mesh pattern. The counter electrode 33 is common to the characters CR1 and CR2.

  In the comparative example configured in this manner, at the boundary between the characters CR1 and CR2, the total wiring width of 3 μm of the edge of the character CR1, 3 μm of the space between the characters CR1 and CR2, and 3 μm of the wiring width of the edge of the character CR2 is 9 μm. The above width is required, and the mesh pattern becomes discontinuous at this boundary. For this reason, when the characters CR1 and CR2 are transparently displayed and scattered, the boundary cannot be visually recognized. However, when the characters CR1 and CR2 are displayed in halftone, the boundary can be visually recognized.

  On the other hand, in the present embodiment, as shown in FIGS. 12 and 13, the function of displaying halftones and the function of displaying characters can be provided on different substrates. That is, when two types of patterns (including characters and cropping frames) that perform halftone display are adjacent, the counter electrode is processed into a predetermined pattern on one substrate, and the upper display is displayed on the other substrate regardless of the pattern. The electrode is processed into a mesh pattern. Thereby, since the mesh pattern does not become discontinuous at the boundary between the two types of patterns, it is possible to prevent the boundary between the two types of patterns from being visually recognized even when the two types of patterns are displayed in halftone.

[5] Routing Example of Wirings 24 and 34 Next, a configuration example in the case of drawing wiring from the lower display electrode, the upper display electrode, and the counter electrode will be described. FIG. 16 is a schematic diagram showing an example of routing of the wirings 24 and 34 provided on the substrates 10 and 11, respectively. For example, the liquid crystal display device 1 is divided into a plurality of segments, and wiring is connected to each segment. In FIG. 16, the wiring 24 for the lower display electrode 20 and the upper display electrode 22 provided on the substrate 10 and the wiring 34 for the lower display electrode 30 and the upper display electrode 32 provided on the substrate 11 are shown as an example. ing. That is, the substrate 10 shows two wirings 24 for the lower display electrode 20 and the upper display electrode 22 for each segment, and the substrate 11 has two wires 24 for the lower display electrode 30 and the upper display electrode 32 for each segment. A wiring 34 of the book is shown.

  In the present embodiment, the lower display electrode and the upper display electrode are disposed on both the substrates 10 and 11. For this reason, the wiring 24 for the lower display electrode 20 and the upper display electrode 22 is arranged on the substrate 10 for some of all the segments, and the lower display electrode 30 and the upper display on the substrate 11 for the remaining segments. A wiring 34 for the electrode 32 can be disposed. Thereby, since the number of wirings arranged on the substrates 10 and 11 can be reduced, the wiring can be easily routed, and the area for routing the wirings on each of the substrates 10 and 11 can be reduced.

  In the comparative example in which the lower display electrode and the upper display electrode are provided only on one substrate, the wiring of all segments is provided on one substrate. For this reason, in the comparative example, the number of wirings provided on one substrate increases, and the area for routing the wirings also increases. On the other hand, in this embodiment, a problem like a comparative example can be avoided.

[6] Effect As described in detail above, in this embodiment, the lower display electrode, the upper display electrode having a mesh pattern, and the counter electrode are provided on both the substrates 10 and 11. Specifically, the first character is configured by using the lower display electrode 20 and the upper display electrode 22 provided on the substrate 10 side, and the counter electrode 33 provided on the substrate 11 side. The second character is configured using the lower display electrode 30 and the upper display electrode 32 provided on the substrate 10 and the counter electrode 23 provided on the substrate 10 side.

  Therefore, according to the present embodiment, halftone display can be performed by using dithering without using an intermediate voltage between 0 V and a high voltage (5 V). Thereby, halftone display over a wide temperature range is possible. Further, since the halftone can be displayed using the binary voltage, the reaction time until the halftone is displayed can be shortened.

  Further, since the polymer dispersed liquid crystal layer 40 is used as the liquid crystal, a plurality of gradations can be expressed without using a polarizing plate or an alignment film. Thereby, the liquid crystal display device 1 capable of reducing the manufacturing cost and miniaturizing can be realized. In addition, a liquid crystal display device that can display brightly with very little loss of light can be realized.

  In addition, wirings connected to the lower display electrode, the upper display electrode, and the counter electrode can be dispersed on the substrates 10 and 11. Thereby, the design man-hour by the wiring pattern routing can be simplified.

  In addition, by designing the shape of the adjacent character on the counter electrode side, it is possible to prevent the mesh pattern of the upper display electrode from becoming discontinuous at the boundary of the adjacent character. Thereby, when the adjacent character is displayed in halftone, it is possible to prevent the boundary between the adjacent characters from being visually recognized.

  Further, since the openings of the upper display electrode are arranged in a staggered arrangement, the upper display electrode has a uniform mesh pattern. Thereby, the display unevenness of a halftone can be suppressed. Further, since the upper display electrode is trimmed along the pattern edge of the character, the display of the pattern edge can be made clear.

  The characters that can be displayed by the liquid crystal display device 1 of the present embodiment include various characters, figures, patterns, and the like.

  The liquid crystal display device 1 of the present embodiment can be applied to liquid crystal screens such as camera viewfinders, watches, binoculars, monoculars, telescopes, and distance measuring devices.

  The present invention is not limited to the above embodiment, and can be embodied by modifying the constituent elements without departing from the scope of the invention. Further, the above embodiments include inventions at various stages, and are obtained by appropriately combining a plurality of constituent elements disclosed in one embodiment or by appropriately combining constituent elements disclosed in different embodiments. Various inventions can be configured. For example, even if some constituent elements are deleted from all the constituent elements disclosed in the embodiments, the problems to be solved by the invention can be solved and the effects of the invention can be obtained. Embodiments made can be extracted as inventions.

  DESCRIPTION OF SYMBOLS 1 ... Liquid crystal display device 10, 11 ... Board | substrate, 12 ... Sealing material, 13 ... Terminal, 20, 30 ... Lower display electrode, 21, 31 ... Insulating layer, 22, 32 ... Upper display electrode, 23, 33 ... Counter electrode 24, 34 ... wiring, 25, 35 ... contact plug, 40 ... polymer dispersed liquid crystal layer, 41 ... drive circuit.

Claims (7)

A liquid crystal display device capable of displaying the first and second characters,
First and second substrates;
A first lower display electrode provided on the first substrate;
A first insulating layer provided on the first lower display electrode;
A first upper display electrode provided on the first insulating layer and having a mesh pattern having a plurality of openings;
A first counter electrode provided on the first insulating layer;
A second lower display electrode provided on the second substrate;
A second insulating layer provided on the second lower display electrode;
A second upper display electrode provided on the second insulating layer and having a mesh pattern having a plurality of openings;
A second counter electrode provided on the second insulating layer;
The first upper display electrode and the second counter electrode are opposed to each other, and the second upper display electrode and the first counter electrode are opposed to each other, and are sandwiched between the first and second substrates. A polymer dispersed liquid crystal layer,
Comprising
The first character includes the first lower display electrode, the first upper display electrode, and the second counter electrode,
The liquid crystal display device, wherein the second character includes the second lower display electrode, the second upper display electrode, and the first counter electrode. The first lower display electrode and the first upper display electrode have the same outer shape,
The liquid crystal display device according to claim 1, wherein the second lower display electrode and the second upper display electrode have the same outer shape. A plurality of first wirings provided on the first substrate and electrically connected to the first lower display electrode, the first upper display electrode, and the first counter electrode;
A plurality of second wirings provided on the second substrate and electrically connected to the second lower display electrode, the second upper display electrode, and the second counter electrode,
The liquid crystal display device according to claim 1, further comprising: A drive circuit electrically connected to each of the first lower display electrode, the first upper display electrode, and the second counter electrode;
The drive circuit controls a first voltage between the first lower display electrode and the second counter electrode, and sets a second voltage between the first upper display electrode and the second counter electrode. 4. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is controlled.   The liquid crystal display device according to claim 4, wherein each of the first and second voltages is binary.   The liquid crystal display device according to claim 1, wherein a diameter of the opening is 100 μm or less.   The liquid crystal display device according to claim 1, wherein the mesh pattern has a staggered arrangement.

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